1. Technical Field
The present disclosure relates to a microphone array control apparatus and a microphone array system that form the directivity of sound in a direction toward a speaker by using sound collected by a plurality of microphone elements.
2. Description of the Related Art
An order input apparatus including a microphone and a loudspeaker is disposed near the position of a vehicle stopped at a drive-through of stores such as a fast-food store or a cafe so that a staff wearing a headset in the store communicates the order content with a speaker (for example, an order placer) who visits the store by vehicle (for example, an automobile). The microphone used in the order input apparatus is a single non-directional microphone or a directional microphone of which the directivity is formed in advance in a predetermined direction. Thus, the sound of the order content collected may be inaccurate due to the sound of the vehicle engine or depending on the surrounding environment.
A sound signal processing apparatus disclosed in Japanese Patent Unexamined Publication No. 2010-16564 is suggested as a preceding technology related to a sound signal processing apparatus in the drive-through system that is provided with an echo canceller which removes echo components generated when the voice of the staff is collected by the microphone in the backward direction.
An echo canceller of the sound signal processing apparatus disclosed in Japanese Patent Unexamined Publication No. 2010-16564, given that the customer side of the drive-through is defined as a near-end side, and the staff side thereof is defined as a far-end side, includes an adaptive filter and a coefficient update controller. The adaptive filter generates a pseudo-echo signal on the basis of a far-end signal. The coefficient update controller causes echo canceller coefficients of the adaptive filter to converge through a coefficient update process. When arrival of the vehicle is detected as a change in the near-end sound collecting environment, the echo canceller changes the coefficient update process so as to decrease the speed of convergence of the echo canceller coefficients according to the passage of time after the detection. The echo canceller decreases the step size of NLMS (learning identification) according to the passage of time and switches the algorithm of the coefficient update process from, for example, recursive least squares (RLS) method to normalized least means squares (NLMS) method so as to decrease, for example, the speed of convergence.
In the drive-through system using a single microphone, however, a problem arises in that it is hard for the staff to listen to the order content of the speaker because the volume of the sound of the vehicle (for example, an automobile) engine is great at a location immediately close to the speaker (for example, an order placer). Furthermore, when noise from a surrounding road, an expressway, or a railroad is great, it is harder for the staff to listen to the order content of the speaker. In addition, the staff may have difficulty in listening to the order content of the speaker depending on whether the vehicle is separated from a predetermined stop position or depending on the different heights of vehicles (for example, automobiles).